Compounds having strong light absorption at specific wavelengths are used in recording layers of optical recording media such as CD-Rs, DVD-Rs, DVD+Rs, and blue laser recording discs and in optical elements of image display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), cathode-ray tube displays (CRTs), fluorescent display tubes, and field emission displays.
Such compounds, when employed as optical elements in image display devices, are used e.g. as light absorbers in color filters, wherein colored pixels are formed on a substrate and white light is passed therethrough to allow originally-monochrome display sections to be displayed in color. Image display devices create color images by combining light in the three primary colors, red, blue, and green, but the beam used for creating the color images includes light that lowers display quality, such as 480- to 520-nm light between blue and green and 550- to 600-nm light between green and red, and also includes 750- to 1100-nm light that possibly causes malfunction of infrared remote controllers. Thus, optical filters are required to have a function of selectively absorbing light in such unwanted wavelengths in displaying color images and/or at the time of operating infrared remote controllers, and also a function of absorbing light ranging from 480 to 500 nm and from 540 to 560 nm in order to prevent reflection and glare of external light from fluorescent lamps etc. In image display devices and the like, therefore, optical filters containing light-absorbing compounds (light absorbers) that selectively absorb light at such wavelengths are used aside from color filters.
In recent years, there has also been a demand for light absorbers that can selectively absorb light at wavelengths particularly ranging from 480 to 500 nm in order to provide display elements with sufficient color purity and color separation and thus achieve high image quality. Such light absorbers are expected to have an extremely sharp light absorption—i.e., a small half width at λmax—and also the ability to maintain their functionalities even when subjected to light and/or heat, for example.
Conventionally, an optical filter has been manufactured by laminating an optical film containing a light-absorbing compound (light absorber) that selectively absorbs light at specific wavelengths onto a transparent substrate, such as glass, by means of an adhesive layer. Such a process, however, results in high cost because of the many steps involved in production and also has difficulty in making the optical filters thin.
Meanwhile, Patent Document 1 discloses a film for electronic displays containing a colorant and carbon black in the adhesive layer. Patent Document 2 discloses an adhesive containing a colorant. Patent Document 3 discloses a filter for displays using an adhesive containing a colorant.
It is, however, difficult to prevent the colorant compounds in the adhesive layers from causing degradation due to light, heat, etc., and there still is no optical filter that can ensure sufficient optical properties.
Further, Patent Document 4 discloses water-based ink containing a color material made by intercalating a dye into a clay. Patent Document 5 discloses a clay mineral composite in which organic cations and an intercalant are held between layers of a clay mineral. Patent Document 6 discloses a fluorescent, layered inorganic-organic composite in which aliphatic quaternary-ammonium ions and a cationic laser colorant are borne on a cation-exchangeable inorganic layered compound. However, nothing has been suggested about the use of such color materials or colored composites in optical filters or about improvement of moisture-and-heat resistance of optical filters by using such color materials or clay mineral composites. Further, Patent Document 7 discloses an optical filter containing a cyanine compound having good absorption properties particularly in the range of 480 to 500 nm. However, it describes nothing about using the cyanine compound in combination with a clay mineral or about using the cyanine compound by forming it into a clay mineral composite.    Citation List    Patent Document
Patent Document 1: JP-A-2003-82302
Patent Document 2: JP-A-2004-107566
Patent Document 3: Japanese Patent No. 3311720
Patent Document 4: JP-A-10-77427
Patent Document 5: JP-A-2-293315
Patent Document 6: JP-A-2004-2491
Patent Document 7: JP-A-2005-194509